NEW YORK -- Online brokerages fighting to keep their share of the U.S. retail market are now competing head-to-head overseas as they look for markets that raise the fewest regulatory flags and allow the swiftest entry.

Charles Schwab Corp., E*Trade Group Inc., Ameritrade Holding Corp. and DLJdirect, the online unit of Donaldson, Lufkin & Jenrette Inc., are setting up joint ventures and alliances in many of the same cities, since...